The present invention relates to a keyboard device of an acoustic piano, an electronic piano or another keyboard instrument and an assembly method thereof, and particularly to though not exclusively a keyboard device provided with an action mechanism or a simulating action mechanism disposed on a chassis with a key support as a key swinging center disposed on a key bed and constituted of a wippen, a jack and a hammer, or to a keyboard device provided with a key support member including a key swing center and a rail member having a hammer swung in accordance with swinging of a key, both members being fixed on a chassis.
In a keyboard device heretofore used in an electronic piano, for example, as shown in FIG. 5, to secure a space of a key 514 (white key shown in FIG. 5) when depressed, a chassis 511 is provided with a flat portion 512 higher than a top face of a key bed 502. The flat portion 512 is provided with a key support 515, centering on which the key 514 is vertically swingably supported. Since the depressed key 514 is biased counterclockwise as shown in FIG. 5 by a spring 516 interconnecting a rear end of the key 514 and a rear end of the chassis 511, the key 514 returns to its original position when released.
Also, a base 528 is attached slightly lower than the chassis 511, and has thereon a push button 537 for detecting depression of the key 514. Two switches are disposed inside the push button 537: when the key 514 is depressed, at the initial stage one of the switches is depressed by an actuator 535 provided under the key 514, and when the key 514 is further depressed, the other switch is also depressed by the actuator 535. Key depressing timing and velocity can be obtained from a difference in switching on or off timing between the two switches.
In the keyboard device, the flat portion 512 of the chassis 511 is extended in a key arrangement direction (vertical to FIG. 5) and in a key back-to-forth direction (right to left in FIG. 5). The key support 515 of each of all the keys (e.g. 88 keys) is provided on the flat portion 512.
A rear end of the flat portion 512 of the chassis 511 is bent vertically downward via a first bent portion 511a, and further bent forward (or backward) via a second bent portion 511b. Therefore, the height of the rear end of the flat portion 512 is defined by the first and second bent portions 511a and 511b. A front end of the flat portion 512 of the chassis 511 is provided with a substantially U-shaped leg portion 513, which defines the height of the front end of the flat portion 512. The flat portion 512 of the chassis 511 is further provided with a reinforcing rib 519. The rib 519 is a leaf member extending in the key back-to-forth direction, and is provided with contact faces 519a, 519b for contacting an underside of the flat portion 512 of the chassis 511 and a reinforcing flange 519c.
In the aforementioned keyboard device, however, the accuracy in height of the key support 515 is influenced by the ending accuracy (accuracy in angle or in dimension of the height) of the first and second bent portions 511a and 511b of the chassis 511. The dimension (area) of the chassis 511 is so large that a large-sized metallic mold is necessary for bending the chassis 511 with a press or the like, and it is difficult to obtain a high accuracy.
On the other hand, for example in a keyboard device for use as an electronic keyboard instrument as shown in FIG. 6, to obtain the same key touch as in an acoustic piano, a simulating action mechanism is provided. Specifically, a hammer 650 is provided behind a rear end of a flat portion 612 of a chassis 611. An action lever 605 for transmitting action to the hammer 650 is passed from the underside of the key backward through a hole 606 connecting a rear end of the chassis 611 and a key bed 602, to transmit action of the key via a wippen 630, a jack 644 and a butt 649 to the hammer 650.
In the aforementioned keyboard device, a raised portion of the chassis 611 between a first bent portion 611a and a second bent portion 611b, the hole 606 for passing the action lever 605 needs to be provided. Further, the hole 606 is required for each hammer, thereby increasing cost. Also, the accuracy in height of a key support is influenced by the bending accuracy of the first and second bent portions 611a and 611b in the same manner as the keyboard device of FIG. 5. Therefore, it is not easy to obtain a high accuracy.
As a keyboard heretofore used in an electronic instrument, a wooden keyboard provided with a hammer or a plastic keyboard provided with a hammer is known. In this keyboard, the hammer is swung directly by a corresponding key. Therefore, a key letting-off effect cannot be obtained. There exists a problem that a touch of an acoustic piano cannot be realized.
To solve the problem and realize the touch of an acoustic piano, as shown in FIGS. 6, 8 or 16, an electronic instrument keyboard provided with a simulating action mechanism has been developed.
In the keyboard device shown in FIG. 6, when a key 614 is depressed to swing counterclockwise in the figure, an action lever 670 provided under the key 614 is also swung counterclockwise centering on a lever swing axis 671 on the chassis 611. Accompanying the swinging, the wippen 630 is swung clockwise arround a wippen swing axis 631 provided on a center rail 660, and the jack 644 pushes up the butt 649 of the simulating hammer 650. The simulating hammer 650 is then swung clockwise. After a jack tail 647 abuts on a regulating button 666, the jack 644 is rapidly swung counterclockwise to be disengaged from the butt 649. Then, the hammer 650 starts its inertial movement. This timing is a letting-off timing. Upon contact with a stopper 663, the hammer 650 swings back. In this manner, the keyboard device shown in FIG. 6 realizes a touch of an upright piano.
The key support 615 as a swing center of the key 614 is supported by a bearing 616 serving as a key support member. As shown in a partially enlarged view of FIG. 11, the bearing 616 has substantially L-shaped legs 618 thereunder. In attachment, after the L-shaped legs 618 are passed through inlets 617 in the chassis 611, the bearing 616 is slid toward the front of the key (to the left in FIG. 11). Thereby, the chassis 611 is placed between the L-shaped legs 618 and the underside of the bearing 616. Under this condition, a stopper piece 620 is fixed with a screw to abut on the rear end of the L-shaped legs 618. In this manner, the bearing 616 is fixed immobile on the chassis 611.
However, in this keyboard device, the stopper piece 620 is provided only for the bearing 616, which adds to cost. Also, attachment of the stopper piece 620 is additionally required, making complicated the operation.
Further, when the key 614 needs to be replaced, by removing the screw from the stopper piece 620, the stopper piece 620 has to be once removed.
In another keyboard device shown in FIG. 8, an action mechanism is the same as the action mechanism of an upright piano, except that a stopper is provided instead of a string. In the keyboard device, when depressed, a key 814 is swung counterclockwise centering on a key support 815. Accordingly, a wippen 830 is swung clockwise centering on a wippen swing axis 831 provided on a center rail 860, a jack 844 pushes up a butt 850a of a hammer 850, and the hammer 850 is then swung clockwise centering on a hammer swing axis 851 provided on the center rail 860. After a tail jack 847 abuts on a regulating button 866, the jack 844 is rapidly swung counterclockwise to be disengaged from the butt 850a. The hammer 850 in turn starts its inertial movement. This timing is a letting-off timing. Upon contact on a stopper 863, the hammer 850 sings back. In this way, the keyboard device of FIG. 8 realizes a touch of an upright piano.
However, a regulating felt on the regulating button 866 for regulating operation of the jack 844 is provided separately from a hammer cushion 868 for regulating an initial position of the hammer 850. Specifically, the former is provided on a regulating rail 861 fixed to the hammer rail 860, and the latter is provided on the hammer rail 869. Therefore, two separate members, the regulating rail 861 and the hammer rail 869 are necessary, thereby increasing cost remarkably.
On the other hand, to adjust the letting-off timing to a predetermined timing, the attachment accuracy of the regulating rail 861 provided with the regulating felt on the regulating button 866 needs to be increased. To set the initial position of the hammer 850 at a predetermined position, the attachment accuracy of the hammer rail 869 provided with the hammer cushion 868 needs to be increased. Therefore, the attachment accuracy of the two different members needs to be increased.
Also in the keyboard devices shown in FIGS. 6 and 8, a key unit U1 is provided separately from an action unit U2. Therefore, when the key unit U1 and the action unit U2 are assembled on the key bed, it is difficult to position these units U1 and U2. Also, after the units are attached onto the key bed, the height of the wippen needs to be adjusted with a capstan screw S for adjusting a key stroke.
In a keyboard device 701 for an electronic keyboard instrument provided with a simulating action mechanism shown in FIG. 16, a button type sensor 737 is provided under a key 714. The sensor 737 is provided with two switches inside. When the key 714 is depressed, one of the switches is depressed to issue an on signal, and when the key 714 is further depressed, the other switch is depressed to issue an on signal. Specifically, the sensor 737 detects respective timings at which the key 714 passes two predetermined positions while the key 714 moves from an initial position to a full stroke position. Based on the signals transmitted from the two switches of the sensor 737, a control device 705 obtains string striking information for producing string striking sound and sound stop information for stopping sound. Specifically, a velocity is obtained as sound intensity from a difference in on-timing between the switches, and sounding is stopped based on the off-timing of the switches.
In the keyboard device 701 for an electronic keyboard instrument, in the same manner as an acoustic piano, the key 714 abuts on a wippen 730 via a cushion C1, and a jack 744 abuts on a butt 750a of a hammer 750 via a cushion C2. Therefore, when the key 714 is depressed at a high speed, these cushions C1 and C2 is once resiliently deformed to store a certain degree of force. Thereafter, when the cushions C1 and C2 recover themselves, the wippen 730 and the hammer 750 act, thereby producing a strong piano sound. After the key 714 is depressed, there is a time lag before sound is produced. These characteristics are unique to an acoustic piano.
However, in the constitution where the key 714 pushes against the button type sensor 737, when the key 714 is rapidly depressed, the cushions C1, C2 are resiliently deformed from when one of the switches inside the sensor 737 is turned on until the other switch is turned on to resist pressure, which produces a resistance force. Therefore, a difference in on-timing between the switches becomes large, and a detected velocity (corresponding to the movement speed of the key) is decreased. An electronic sound is produced with intensity in accordance with the velocity. No strong sound is disadvantageously produced like an acoustic piano. Also, there arises no time lag until sound is produced like an acoustic piano. Specifically, in the keyboard device 701, the aforementioned characteristics peculiar to an acoustic piano cannot be reproduced precisely.
Therefore, there exists a desire for development of a keyboard device for an electronic piano which can reproduce the characteristics peculiar to an acoustic piano.
It is proposed in the keyboard device 701 that the generation of electronic sound is controlled in accordance with the movement speed of the hammer 750, not the movement speed of the key 714. The hammer 750 has the largest inertial moment in the swingable members of the action mechanism. After the key 714 is depressed, the hammer 750 most remarkably withstands before starting swinging. Therefore, by generating an electronic sound in accordance with the movement speed of the hammer 750, the aforementioned characteristics peculiar to an acoustic piano can be remarkably precisely reproduced. Specifically, for example, a sensor, the same as the button type sensor 737, to be depressed by the hammer 750 is provided for detecting the hammer 750 at two places between a standstill position and a simulating string-striking position of the hammer 750.
In the keyboard device 701, in the same manner as an acoustic piano, when the key 714 is depressed from its standstill position to its full-stroke position, the hammer 750 is swung from the standstill position (shown by a solid line in FIG. 16), midway let off and swung to the simulating string-striking position (shown by a two-dotted line in FIG. 16). Thereafter, the hammer 750 swings back. If the key is not released while the hammer 750 swings back, a catcher 754 is supported by a back check 743 at a backstop position (shown by a dotted line in FIG. 16). If the key is released, the hammer 750 is received by a hammer rail 768 at its standstill position.
Consequently, when generation of an electronic sound is controlled in accordance with the movement speed of the hammer 750, to precisely detect sound stop information, the sensor needs to be switched on or off precisely at the backstop position and the standstill position. Since the positions are close to each other, however, it is technically difficult to switch on or off the sensor precisely. To solve the problem, it is necessary to provide a separate switch to be turned on or off, for example, by the key for obtaining sound stop position. There arises a problem of increasing cost.
Also in the keyboard device 701, a hammer skin HS (i.e. the cushion C2) is placed on the butt 750a of the hammer 750 for absorbing shock of collision with the jack 744, inhibiting collision sound from generating and smoothly sliding on the jack 744. Also, a catcher skin CS is placed on the catcher 754 for absorbing shock arising when the catcher 754 is received by the back check 743 and inhibiting collision sound from generating.
However, since the hammer skin HS is a separate member from the catcher skin CS, a cushioning material has to be cut into the separate members to be placed, thereby increasing cost.
Further, when the key 714 is depressed, a capstan button 716 provided behind a key support 715 pushes up a felt F of the wippen 730. Thereby, the jack 744 is operated and the hammer 750 simulatively strikes a string. In this manner, the capstan button 716 has an important function. To provide the capstan button 716, the rear side behind the key support 715 of the key 714 requires a length. It is structurally difficult to shorten the key 714.